Recent research shows that the marsupials might be the key to developing an antivenom that could not
only save people from snake bites but from attacks by scorpions and from plant and bacterial toxins as well given that their nicest thing they have been doing for man is eating eat a lot of ticks.
According to a press release about the research, opossums are apparently immune to the venom from snake bites. This has gotten researchers curious about why that is so and whether they could harness the opossum’s antivenom properties for use on humans. The first bit of research on the topic was done in the 1940s and was followed up again the early 1990s, but current researcher Claire F. Komives from San Jose State University says no one followed up on the studies to create a working antivenom therapy since then.
Mammalogists Sharon Jansa and Robert Voss have just published a study of one blood protein that may underlie opossums’ resistance to venom. The venom of pit vipers like rattlesnakes and water moccasins targets the blood clotting system—one of the unpleasant effects of a snake bite is internal hemorrhage. So Jansa and Voss examined the evolution of a venom-targeted clotting protein called von Willebrand Factor, or vWF, comparing it across the entire family of opossums, the didelphidae.
Since the evolutionary origin of the family, the vWF of opossum species that prey on snakes has accumulated more changes than vWF in non-snake-eating species. That’s circumstantial evidence for the effect of natural selection continuously acting on vWF over millions of years. Jansa and Voss picked out several specific changes that are unique to snake-eating opossums, and found that they’re associated with a region of vWF that is known to bind with one of the toxins in pit viper venom.
The authors suggest that opossums may have been engaged in an evolutionary “arms race” against snake venom toxins since they first developed a taste for rattlesnake. In other words, not only is the opossum not unchanged since the early history of mammals, one of the traits that has changed continuously since then may be the very feature that piqued Kilmon’s interest being that a field
observations and laboratory trials showing that opossums tolerate snakebites without visible ill effect. A natural bite was observed in the field by a 160 cm eastern diamondback on an adult opossum, Didelphis virginiana. The opossum displayed no apparent distress and this suggested a remarkable tolerance by that animal to envenomation. In order to ascertain if an actual envenomation did take place, Kilmon conducted field experiments by manually causing snakes to inflict actual bites on captured opossums. None of the bites caused visible signs of distress to the opossums. Kilmon brought possums back to the lab, anesthetized them, hooked them up to heart monitors, and “inflicted” bites on them from diamondback and timber rattlesnakes, water moccasins, and at least one cobra. “None of the five opossums,” he wrote, “developed observable local reactions other than trauma attributable to fang penetration and none developed observable systemic effect, exhibiting negligible alteration of heart rate and respiration.”